The present invention relates to a method and device for regulating the population of animals, and in particular, is directed to a system using a sterilant projectile which permanently and/or temporarily sterilizes an animal.
Overpopulation of feral animals such as wild horses, burros, deer and elk in North America, as well as several African species world-wide, has become a problem of great significance. Many herds now share environmental space with human populations, making harvest of such animals for meat using high-powered weapons dangerous. Further, human populations have reduced or eliminated natural predators in their attempts to protect domestic livestock which share the same ecosystems.
Deer may be one of the most valued and viewed mammalian wildlife species in North America. Millions of outdoor visitors savor the sights of deer and try to capture them on film. State fish and game agencies regard deer as a renewable, harvestable resource for viewing and hunting. Sport hunters annually bag about 1 million mule deer and 2 million white-tailed deer. However, deer may cause profound damage by browsing on garden vegetables, flowers, ornamental bushes, and crops. Collisions of automobiles with deer in some areas of the country have increased to alarming levels. In some national parks, deer are a natural resource that may have to be managed. About 50 units in the National Park System in the eastern United States and in the Midwest have identified possible or potential conflicts between the management goals and objectives of parks and white-tailed deer. Various parks with large populations of elk and burros, as well as federal lands which support feral horse populations, have similarly experienced animal management difficulties.
Since the late 1950s, densities of white-tailed deer in many areas of the eastern United States have increased to previously unattained levels and the distribution across the former range has changed drastically. The causes of the changes are various. For example, continuing fragmentation of forested lands into agricultural, suburban, and other types of anthropogenic lands creates favorable habitats with year-round reliable food sources. This increase in food supply has been accompanied by a decrease in historical controls of deer populations. Animals like wolves, coyotes, mountain lions, and bobcats that prey on deer usually do not survive urbanization and have been extirpated in many areas. Restrictions on hunting seasons, bag limits, and available lands for public hunting have also been cited as factors.
Beyond the park service, countless communities face increasing problems with deer overpopulation. Typically, such problems engender inflammatory debate between animal lovers, wildlife or ecology management groups, and hunters. Moreover, there are relatively few options to control deer overpopulation available in urban areas. The park service document lists the following available methods:
1. Live Removal and Relocation for the reduction of large populations are usually not desirable because of the high cost, lack of acceptable release sites, and high mortality of the relocated animals.
2. Removal by Public Hunting can be done only in units where it is specifically authorized by the U.S. Congress. Only in these few units may hunting by the public be used to control the density of deer. Hunting in urban areas, even with muzzle loaded or other shotguns or by bow and arrow is impractical for safety reasons.
3. Direct Reduction by Shooting by National Park Service personnel can be done under provisions of the National Park Service Organic Act and the National Park Service Management policies. It is the least desirable alternative.
4. Fertility Control (Contraception) reduces birthrates but does not reduce the sizes of existing populations. It must therefore be implemented before the populations surpass established acceptable levels. If a population reaches an excessive size, fertility control may be implemented but must be accompanied by a reduction of the population size by other means.
5. Fencing may be used to protect threatened and endangered plants from browsing by deer, to prevent deer from crossing roadways, and to minimize the effects of deer on woodlots, agricultural areas, and developed areas. Fencing for the mitigation of harm from deer is limited to small areas because fences can prevent desired migration or dispersal of other animal species. Furthermore, the construction and maintenance of fences is labor intensive and expensive, and fences may be an unacceptable intrusion into the cultural aesthetic values of some parks.
6. Landscape-Agriculture-Timber Management can be designed to create less than favorable habitats for deer with unpalatable plant species, wide open spaces, or severely thinned forest habitats. Such management may, however, be too costly or conflict with the mandated objectives of a park or overall management of adjacent areas.
7. Repellents are compounds or substances that are sprayed on or attached to vegetation to repel browsing by species such as deer. No single repellent is effective for a wide range of plants and conditions. Research revealed that the efficacy of repellents is low and that repellents at best are an interim solution under limited circumstances. Therefore, there exists a long felt and unsolved need to provide methods for controlling over populations of feral animals which are practical, cost effective, socially acceptable and are capable of being administered by governments while maintaining hunting recreation to accomplish agency objectives.
To deal with the problems as set forth above, the present inventors have devised an alternative form of sterilization which can be modified to either temporarily or permanently (depending on the desired result) sterilize an animal. The fertility of all mammals, including man, is controlled by a single hormone, Gonadotropin Releasing Hormone (GnRH) which is produced by the hypothalamus and secreted in a pulsatile fashion. Paradoxically, continuous administration of the hormone leads to pituitary desensitization and a resultant decrease in the gonadotropins FSH and LH which are crucial to control of both ovulation and spermatogenesis in females and males respectively. Potent agonists and antagonists of the GnRH decapeptide are available and have been successfully used in human biology to control prostate cancer, breast cancer, and to treat infertility, endometriosis, and precocious puberty.
For wild animals, this approach has several potential advantages over other methods of contraception. These include:
1) a single treatment should permanently or temporarily sterilize an animal;
2) the same treatment should be effective in both males and females and in different mammalian species;
3) GnRH agonist or GnRH-toxin conjugates is metabolized from the body within a few days of treatment;
4) The proteinaceous nature of GnRH agonist and by GnRH-toxin conjugates eliminates the possibility of passage through the food chain to humans or other non-target species;
5) The small volume required for effective contraception facilitates microencapsulation and administration by diodegradable projectiles.
6) Protein conjugates of GnRH can induce autoimmunity to GnRH adding to the sterilizing short and long term potential.
One agent of the present invention relates to a new weapon/biology system that can be used worldwide in controlling animal populations which overpopulate habitats occupied by humans while avoiding the necessity of killing animals. Moreover, the system of the present invention may give rise to an entirely new sport, similar to xe2x80x9ccatch and releasexe2x80x9d fishing, which could enhance or complement the hunting experience in areas where more traditional methods of harvesting game animals are not feasible.